In this time of abundant food, calorie expenditure during exercise or daily activities has been recognized as one important index for maintaining health. Accordingly, the determination of calories expended is very significant. The standard total number of calories expended daily may vary widely, from a minimum of 1,000 kcal for a 1-year old child to a maximum of 3,800 Kcal for a 17-year teenager.
When measuring calorie expenditure, accuracy of within about 5% of the minimum value is considered necessary. Accordingly, the measurement error must be within 50 kcal.
Calorie expenditure measuring devices, such as th at disclosed in Japanese Patent Application Hei 8-52119 for example, has been proposed as devices for measuring the body's calorie expenditure. Such calorie expenditure measuring devices record the subject's sex, age, height, body weight, body fat ratio, and other constants in advance, as well as a table of standard basal metabolism values per unit of surface area on the body. These devices also use formulas for calculating the calorie expenditure when the subject is at rest or is exercising. When measuring the calorie expenditure, the measured pulse rate value and each of the constants cited above are substituted into formulas according to whether the subject is resting or exercising. Calorie expenditure is then calculated by referring to the aforementioned table of standard basal metabolism values.
However, the conventional devices for measuring calories expended described above have the following problems.
First, these conventional calorie expenditure measuring devices are provided with a comparison and determination device which determines the calculation formula to be used by comparing the measured pulse rat e and the "pulse rate threshold value (pulse rate when standing quietly)". However, it is well known that the pulse rate may rise due to various factors, including stress. Thus, since these devices determine the calculation formula which will be used according to the pulse rate only, they cannot discriminate between whether an increase in the pulse rate is due to factors other than increased activity, such as stress, or because the subject is actually exercising. As a result, calorie expenditure may be incorrectly calculated.
Second, in recent years it has come to be understood that there are a variety of physiological parameters, pulse rate included, that are subject to cyclical variation (daily, monthly or annually). For this reason, if the calculation of calorie expenditure is not corrected for this variation, then the accuracy of the calculation is suspect. Conventional calorie expenditure measuring devices do not take into consideration the fact that pulse rate varies cyclically, so that accurate measurement of calorie expenditure is difficult.
Thus, measurement accuracy of within 50 kcal as described above cannot be obtained using these conventional calorie expenditure measuring devices.